Hot-rolled steel strip, hot strip of stainless steel or titanium alloy and the like notoriously have relatively difficult to remove scale layers adherent to them and of varying hardness. As a result, the strip surface is generally nonhomogeneous.
To facilitate working of the steel strip by cold rolling, such steel strip is generally initially annealed. The annealed steel strip can then be subjected to a preliminary descaling operation to facilitate removal of the scale before the strip is pickled. The shot-blast descaling operation results in a roughening and homogenization of the strip surface.
The annealing, shot-blast descaling and pickling are carried out in a common processing line. As a consequence, the thus treated steel strip is wound up into a coil and supplied to a separate processing line containing the cold-rolling frames or mills. The cold-rolling operation results in a reduction of the strip thickness to the desired final thickness and amounts to a size calibration of the strip concurrently with a smoothing of the strip surfaces and a compacting of the strip.
The strength of the steel strip increases sharply with the cold-rolling operation so that its deformability is correspondingly reduced. As a result, cold-rolled steel strip must be subjected to a further annealing operation in which the strength of the steel strip is lowered by a recrystallization phenomenon and the deformability of the strip is increased. If the annealing is not carried out under a protective gas (blank annealing), annealing scale develops on the strip surface and must be again removed by a pickling operation. The annealing and pickling are again carried out in another treatment line, i.e. a so-called cold-strip line. The fabrication process just described is relatively time-consuming, energy-intensive and expensive because of the personnel costs.
In another known process, the hot strip is cold-rolled without pretreatment and after the cold-rolling is subjected to annealing and pickling.
In this case, the increased surface roughness must be acceptable since without it, the difficult to remove scale would remain to be rolled into the strip surface if the pretreated hot strip is to be subjected to cold-rolling in a continuous processing line (compare U.S. Pat. No. 5,197,179).